Social-ecological portfolio effects in ecosystem service provision, the case of commercial Pacific salmon fisheries in Canada

Human societies depend on stable ecosystem services, which are often stabilized by the ecological portfolio effect arising from biodiversity. Yet, whether this ecological stability propagates to the socio-economic dimensions of an ecosystem service is poorly understood. This study provides a social-ecological portfolio analysis of an ecosystem service by examining the provisioning service provided by commercial Pacific salmon ( Oncorhynchus ) fisheries in British Columbia, Canada. We used the Essential Ecosystem Service Variables (EESV) framework to analyze longitudinal monitoring data across multiple ecosystem service dimensions: ecological supply (abundance), use (catch), demand (price), instrumental value (landed value), and anthropogenic contribution (effort). We quantified portfolio strength and synchrony at two scales: a provincial multi-species portfolio (driven by species diversity) and regional species-level portfolio (driven by regional diversity). At the provincial scale, we found that species diversity provided a stabilizing portfolio effect across ecological and socio-economic dimensions. However, the underlying dynamics in species pair synchrony were not uniform. For example, we found high synchronicity in the Chinook–Coho pair for ecological supply , and Coho–Pink for instrumental value . This difference suggests that social and economic processes provide an additional, portfolio buffering effect. At the species-level, regional portfolios varied greatly: Pink was the most stable throughout social-ecological dimensions, whereas Chinook showed a weak, synchronous portfolio in ecological supply , highlighting potential vulnerability. Our findings suggest that, while biodiversity underpins overall social-ecological stability, specific ecological dynamics, such as the synchronicity of Chinook dynamics, may threaten ecosystem service stability. This approach highlights the importance of integrated social-ecological monitoring to identify and manage risk.